Eric Semail is graduated in 1986 from the Ecole Normale Superieure, in France. He received Ph.D. degree in 2000 on « Tools and studying method of Multiphase Electrical systems, Generalization of the space vector theory ». He became Associate Professor at Engineering school of ENSAM in 2001. In Laboratory of Electrical Engineering of Lille (L2EP) in France, his fields of interest include design, modelling and control of multi-phase drives (converters and AC Drives). More generally he studies Multi-machine and Multi-converter systems.
Abstract: This paper deals with fault tolerant multiphase electrical drives. The quality of the torque of vector-controlled Permanent Magnet (PM) Synchronous Machine supplied by a multi-leg Voltage Source Inverter (VSI) is examined in normal operation and when one or two phases are open-circuited. It is then deduced that a seven-phase machine is a good compromise allowing high torque-to-volume density and easy control with smooth torque in fault operation. Experimental results confirm the predicted characteristics.
Abstract: This paper deals with easy to implement control strategies when a seven-phase Axial Flux Permanent Magnet machine (AFPM) supplied by a seven-leg Voltage Source Inverter (VSI) is in fault operation mode. Using a vectorial multi-machine description, a seven-phase machine presenting a heightened ability to be controlled with one or two open-circuited phases has been designed. The machine is first presented and experimental results are provided when one or two phases are open-circuited. Based on a vectorial approach, new current references are calculated to avoid high torque ripples.
Abstract: In this paper, a 7-phase Axial-flux Double-rotor Permanent Magnet Synchronous Machine is studied using analytical and Finite Element methods. This type of machine shows a higher sensitivity to the inductance harmonics and electromotive force (emf) compared with the 3-phase machines. So, the conventional analytical modeling method, in which only the first harmonic is taken into account, leads to significant errors in the determination of the control parameters, e.g. the frequency of Pulse Width Modulation Voltage Source Inverter. A multi-machine model explains the reasons for this sensitivity and a more sophisticated analytical method is used. Results are compared with those obtained by the 3-D FEM.
Abstract: This paper presents the equivalence of multi-phase machines with a set a of 1-phase and 2-phase machines with no magnetic couplings. Two cases are then studied. First, a 5-phase machine supplied by a Voltage Source Inverter(VSI) is analyzed. Then, a model is established for a single 5-leg VSI supplying two 5-phase machines whose windings are connected in series.
Abstract: Multi-phase drives are more and more often used in industry, especially for high-power applications [17, 18, 20]. Space Vector Modulation (SVM) is now widely implemented and possesses many advantages over carrier-based pulse width modulation (PWM): � natural overmodulation implementation; � easy solution for saturation treatment; � fast and convenient to compute; � easy implementation of switching constraints for example to reduce harmonic currents [19]. Many authors proposed SVM VSI applied to multi-phase drives. For example, [2] and [15] have chosen instantaneous vectors to control dual 3-phase induction machines with low generated harmonic currents, [4] and [6] to control 5-phase machines. The initial space is split onto orthogonal subspaces (d-q and zero-sequence) and the initial reference vector can be expressed at any sampling time in terms of several reference vectors, each one belonging to one subspace (plane and/or line). Each reference vector is located onto a sector, bounded by two active vectors, and decomposed onto these vectors. Once the two vector components are known, duty ratios are determined. Then, zero vectors are chosen and switching sequencing is imposed. Due to the high number of phases, a high number of sectors exist and the location of the different reference vectors leads to a great computational requirement (Fig. 1a). Using the equivalence between a multi-phase machine and a set of fictitious one-phase or two- phase machines which are magnetically independent but mechanically and electrically coupled [1, 13], we propose a new fast algorithm to compute the duty cycles of each VSI leg. This algorithm, based on a vectorial approach of inverters developed in [3, 5, 7, 22], thereby reduces computation time and allows to use low computational requirements. This paper shows that, compared to classical techniques [9, 10, 11, 12], it is no more necessary to find the location of the reference vectors to get explicitly the duty cycle of each leg. Fig. 1 shows the difference between classical algorithm (Fig. 1a) and proposed one (Fig. 1b). This proposed technique is at first illustrated on a 3-phase drive. Geometrical representations allow then to establish links with usual 3-phase SVM. The implementation of the proposed SVM is achieved in the vector control of a 5-phase drive. Experimental results are presented and confirm the theoretical approach.
Abstract: A generic and simple control method is suggested for any multileg voltage-source-converter. A specific coding yields an inversion table allowing a fast practical implementation. Phase-to-phase voltage references have to be defined for such a table. This original control strategy is validated by experimental results for two-leg, three-leg, four-leg, and five-leg structures supplying balanced and unbalanced multiphase loads
Abstract: This letter describes a vectorial formalism useful for studying polyphase systems. For that purpose, mathematical tools as the concepts of barycenter, linear application and kernel are introduced. This formalism generalizes the Space Vector Theory (SVT). A two levels three legs voltage-source inverter (23VSI) is studying to prove this property. At the end, a graphic representation of the homopolar component is presented.
Abstract: This paper presents an analytical multi-physic modeling tool for the design optimization of a new kind of naval propulsion system. This innovative technology consists in an electrical permanent magnet motor that is integrated into a duct and surrounds a propeller. Compared with more conventional systems such as pods, the electrical machine and the propeller have the same diameter. Thus, their geometries, in addition to speed and torque, are closely related and a multidisciplinary design approach is relevant. Two disciplines are considered in this analytical model: electromagnetism and hydrodynamics. An example of systematic design for a typical application (a rim-driven thruster for a patrol boat) is then presented for a set of different design objectives (efficiency, mass, etc). The effects of each model are commented
Abstract: Risk of irreversible magnet demagnetization during short-circuit fault is analyzed in case of an axial-flux dual-rotor machine, using a three-dimensional finite-element method (3D-FEM). In order to validate the numerical model, calculated waveforms of the currents are compared with experimental results for short-circuit at low speeds. Then currents and magnetic flux density inside the magnets are computed for short-circuit at higher speeds in order to predetermine the maximum admissible speed for the machine
Abstract: This paper investigates an electrical drive composed of a four-leg voltage source inverter and a three-phase starconnected surface permanent magnet synchronous machine. The fourth leg of the inverter is clamped to the neutral point of the machine. We find the current references reading to smooth torque and maximum torque per ampere operation in the presence of a third harmonic electromotive force component. We further analyze the advantages of the proposed topology in terms of torque increase and dc-link voltage requirements. Design aspects are briefly discussed.
Abstract: This paper deals with the modeling and the control of a new high power 12V Integrated Starter Alternator (ISA). This system is used to bring micro-hybrid functions to standard Internal Combustion Engine (ICE) vehicles. The drive is composed of a seven-phase synchronous claw-pole machine with separate excitation, supplied with a seven-leg Voltage Source Inverter (VSI) designed for low voltage and high current. The system is modeled in a generalized Concordia frame and a graphical description is used to highlight energetic properties of such a complex system. A control scheme is then deduced from this graphical description. Two controls are achieved in generator mode and compared: one is using the VSI in a square-wave mode, the other in a Pulse Width Modulation (PWM) mode. Experimental results are provided
